DETERMINING THE AMOUNT OF SHALE IN
FINE AGGREGATE

SCOPE

This test method covers the procedure for the
approximate determination of the shale content in fine aggregate.This test method
is the field procedure for Laboratory Test Method 209.

PROCEDURE

A. Apparatus

Balance having a capacity of not less
than 1000 g and sensitive to at least 0.1 g

A strainer with openings smaller than
#16 sieve (1.18 mm)

3.Two bowls of
sufficient capacity

4.A solution of zinc
chloride (ZnCl2) having a specific gravity between 1.950 and 1.999
at 70°F (21°C)

NOTE: To
prepare one gallon of solution, slowly add 12.5 lb. (5670 g) of technical grade
zinc chloride to 4.75 pt. (2248 g) of water with constant stirring. The zinc
chloride is added slowly to all the needed water to avoid generating excessive
heat during the dissolving process. When all zinc chloride is in solution, cool
to 70°F (21°C) and measure specific gravity with a hydrometer. If the sp. gr.
is below 1.95, add zinc chloride in 0.5 lb. (227 g) increments until the sp.
gr. of the solution is at least 1.95 at 70°F (21°C). It may be necessary to
heat the original solution slightly in order to dissolve additional zinc
chloride in a reasonable time.

CAUTION: There is no
particular hazard from the fumes of the zinc chloride

solution, but protective
clothing should be worn. This includes gloves, goggles, and face shield. Mix in
a well-ventilated area.

5.Drying oven or hot
plate

6.Mixing spoon

B. Sample
Preparation

1. Select a
representative sample by appropriate methods detailed in Materials IM 301 and
336. The weight of the representative sample shall be large enough to yield at
least 500 grams of dry material passing the #4 (4.75mm) sieve.

2. Sieve the
representative sample over the #4 (4.75mm) sieve unless the material is Fine
Aggregate for use in PC Concrete. In this case, any material retained on the #4
(4.75mm) sieve is also part of the test sample.

3.Dry the test sample
to a constant weight, allow to cool, weigh, and record as the Original Dry
Weight of the Test Sample.

4.Sieve the test sample
over the #16 (1.18mm) sieve. Discard the material passing this sieve and
subject the test sample to the test procedure.

NOTE: The test sample may
be accumulated from a completed sieve analysis. This would include the material
retained on the #8 (2.36mm) and #16 (1.18mm) sieves, as well as any material
retained on the #4 (4.75mm) sieve if the intended use is PC Concrete.

The Original Dry
weight of the test sample would then be the difference between the Original Dry
Weight of the sieve analysis sample and the total of the weights retained on
and above the #4 (4.75mm sieve). (The test sample weight of Fine Aggregate for
PC Concrete would be the Original Dry weight of the sieve analysis sample.)

C. Test
Procedure

1.Pour the zinc chloride
solution into a mixing bowl until the volume of the liquid is at least 3 times
the absolute volume of aggregate.

2. Stir the fine
aggregate sample into the solution until all particles are coated.

3. Pour the liquid
off into a second container, passing it through the strainer. Make sure that
only the floating pieces are poured off and that none of the fine aggregate is
decanted onto the skimmer.

4. Return to the
first container the liquid that has been collected in the second container and
after further agitation of the sample by stirring, repeat the decanting process
just described until the sample is free of floating pieces.

5. Thoroughly wash
the removed particles in the strainer to remove the zinc chloride. Dry to a
constant weight (mass) in an oven at a temperature of 230 ± 9°F (110 ± 5°C) or
on a hot plate at a low heat setting. Weigh to the nearest 0.1 g.

D. Calculations

1. Calculate the
percentage of shale (and other low specific gravity materials) by the following
formula:

*This mass (weight)
includes the material passing the #16 sieve (1.18 mm) and represents the total
sample mass (weight) of the fine aggregate. Report the result to the nearest
0.1 percent.